US4973608A - Process and apparatus for charging a liquid reactant with gas - Google Patents

Process and apparatus for charging a liquid reactant with gas Download PDF

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Publication number
US4973608A
US4973608A US07/316,381 US31638189A US4973608A US 4973608 A US4973608 A US 4973608A US 31638189 A US31638189 A US 31638189A US 4973608 A US4973608 A US 4973608A
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United States
Prior art keywords
gas
reactant
tank
gassing
stirrer
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Expired - Fee Related
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US07/316,381
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English (en)
Inventor
Kurt Krippl
Klaus Schulte
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Bayer AG
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Bayer AG
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Assigned to BAYER AKTIENGESELLSCHAFT reassignment BAYER AKTIENGESELLSCHAFT ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: KRIPPL, KURT, SCHULTE, KLAUS
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
    • B29C67/24—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 characterised by the choice of material
    • B29C67/246—Moulding high reactive monomers or prepolymers, e.g. by reaction injection moulding [RIM], liquid injection moulding [LIM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B7/00—Mixing; Kneading
    • B29B7/74—Mixing; Kneading using other mixers or combinations of mixers, e.g. of dissimilar mixers ; Plant
    • B29B7/7404—Mixing devices specially adapted for foamable substances
    • B29B7/7409—Mixing devices specially adapted for foamable substances with supply of gas
    • B29B7/7414—Mixing devices specially adapted for foamable substances with supply of gas with rotatable stirrer, e.g. using an intermeshing rotor-stator system
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B7/00—Mixing; Kneading
    • B29B7/74—Mixing; Kneading using other mixers or combinations of mixers, e.g. of dissimilar mixers ; Plant
    • B29B7/7404—Mixing devices specially adapted for foamable substances
    • B29B7/7433—Plants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2075/00—Use of PU, i.e. polyureas or polyurethanes or derivatives thereof, as moulding material

Definitions

  • This invention relates to a process and an apparatus for charging at least one liquid reactant with gas, especially in small quantities, for the production of foams, and in particular polyurethane foams.
  • the reactant is continuously introduced into a gassing tank which is under pressure and in which a gas cushion is maintained in the upper region. Gas is absorbed from the upper region via a hollow stirrer which disperses the gas in the liquid which is situated below the stirrer in the lower region of the gassing tank.
  • the reactant, now charged with gas is then removed from the gassing tank for further processing.
  • the best way to assist the foaming reaction is to charge the component with as much gas as possible.
  • the polyol component is charged with 20 to 70 volume % of gas.
  • a reaction mixture which is charged with gas has improved flow properties, expands more uniformly and in the mold exerts a pressure from within which prevents the formation of surface defects such as cavities in the finished molded product.
  • the hollow stirrer is shut off when the density reaches the required value and is switched on again as soon as the density rises above this value.
  • This technique is unsuitable for dispersing small quantities of gas in a component because the amount of gas introduced cannot be controlled with sufficient accuracy.
  • the gassed component in the storage tank must be stirred to maintain homogeneity but stirring causes small gas bubbles to unite to form larger bubbles so that the component contains a wide range of sizes of bubbles. This is particularly disadvantageous for cell formation.
  • a continuous process has been described, a so-called on-line process (German Offenlegungsschrift No. 3,434,443), in which a gassing container is connected to the conduit leading from the storage tank to the mixing head.
  • a hollow stirrer absorbs gas from an air cushion in the upper region of the gassing tank.
  • This gassing tank is designed as a continuous flow tank, i.e. the component which has not yet been gassed is introduced into the lower part of the container and removed from the middle region after it has been charged with gas, but a true circulation is not maintained. In this process, the component charged with gas has contact with the gas cushion.
  • FIG. 1 is a schematic illustration of the layout of the apparatus.
  • FIG. 2 is a section taken on the line A--B of FIG. 3, showing a modification of the opening of the supply duct for the components into the gassing tank.
  • FIG. 3 represents a section taken on the line C--D of FIG. 2.
  • FIG. 4 represents a section taken on the line E--F of FIG. 5 of a second variation of the opening of the supply duct.
  • FIG. 5 represents a section taken on the line G--H of FIG. 4.
  • FIG. 6 represents a section taken on the line I--K of FIG. 7 of a third variation of the opening.
  • FIG. 7 represents a section taken on the line L--M of FIG. 6.
  • the liquid reactant which is as yet uncharged with gas is introduced into the gassing tank at a point just below the substantially constant liquid level of the reactant.
  • the reactant When the reactant has been charged with gas, it is removed at a point below the region where gassing takes place.
  • a three-layered arrangement is thereby established and maintained in the gassing tank so that the layer of gas is separated from the layer of gas charged component by the layer of uncharged component.
  • the gas charged component is thus maintained at a density corresponding to the desired gas content, taking into account any significant starting conditions, such as the original density, the temperature and the pressure. If necessary, this density is maintained by suitably varying the stirrer speed.
  • the as yet ungassed intermediate layer which does not, of course, have a sharp boundary with the gassed layer, prevents any diffusion between the gas cushion and the said component and thereby eliminates a troublesome source of error encountered in the known processes. It is essential to take into account the starting conditions, and in particular the density, pressure and temperature. Using the ungassed or completely degasified component under various conditions of pressure and temperature as a basis, any desired gas content can be corollated with the corresponding density. The difference between the original density and the density of the gas charged component is a measure of the additional quantity of gas dispersed in the component. If fluctuations in the initial density, pressure and temperature occur in the course of the process, then the speed of rotation of the stirrer is adjusted to keep the gas content constant over the entire operating time.
  • Changes in the initial conditions need only be taken into account if they are large enough to be significant. This is generally the case when the gas content is low. After the liquid reactant has been charged with gas and, as far as possible, the charged component should undergo no pressure drop until it has been mixed with the second reactant.
  • the interface between the gas cushion and the reactant is preferably kept as small as possible. Diffusion is thereby almost completely prevented. At the same time, equalization of pressure between the gas cushion and the reactant in the gas tank is possible.
  • the liquid reactant is shielded against the rotation of the stirrer shaft. This prevents the formation of a funnel which could draw uncontrolled amounts of gas into the reactant.
  • Introduction of the component which is not yet charged with gas is preferably carried out by continuously renewing the whole layer of reactant situated at the interface with the gas cushion. This is achieved by introducing the component as a very wide, flat stream, and optionally by using several inlets.
  • the hollow stirrer is operated at speeds of up to a maximum of 1200 revolutions per minute. It has surprisingly been found that against all expectations, the gas is dispersed much more finely in the reactant if the speed of rotation of the stirrer is not too high. A narrow range of bubble sizes is thereby advantageously achieved.
  • a stream which is produced only by the inflow, the outflow and the action of the hollow stirrer but is otherwise undisturbed is advantageously maintained in the gassing tank. This is achieved by dispensing with the flow breaker which has conventionally been used in gassing tanks.
  • the ratio of the diameter of the gassing tank to the diameter of the circle described by the hollow stirrer should be such that the contents of the tank do not take part in the rotation.
  • the liquid level of the reactant in the gassing tank is preferably kept constant, at least between two limiting values, by the supply of gas. Whether the level is kept as constant as possible or is kept between two limiting values is primarily a question of technical outlay but the limiting values should be sufficiently close together not to constitute sources of error.
  • the new apparatus for charging at least one liquid reactant with gas is based on a gassing tank which is to be attached to a conduit leading from a storage tank to a mixing head.
  • the gassing tank is equipped with a hollow stirrer which has an intake opening in the upper region within the gassing tank and stirrer blades with gas outlet openings in the lower region of the gassing tank.
  • a gas supply pipe opens into the upper region of the gassing tank.
  • the novel feature of the present invention is that the gassing tank has a filling level regulator for controlling the liquid level of the reactant, which regulator is associated with an activator drive of a shut off valve in the gas supply duct by way of a pulse lead.
  • the opening of the feed pipe for the as yet ungassed reactant is situated just below the liquid level of the reactant.
  • the outlet opening into the discharge duct for the reactant charged with gas is situated below the stirrer blades.
  • Density measuring instruments are arranged both in the inlet pipe and in the discharge pipe, which measuring instruments are connected by pulse leads to a computer and control apparatus which in turn is connected to the speed adjustable drive of the hollow stirrer by a pulse lead.
  • the filling level regulator serves to replace the spent gas while the rate of inflow of ungassed reactant remains substantially constant.
  • the opening of the inlet pipe at a level just below the liquid level ensures that the uppermost layer is constantly replaced. Since the opening into the discharge pipe for gassed reactant is situated below the hollow stirrer, preferably centrally in the base of the container, the gassed reactant can no longer come into contact with the gas cushion and optimum flow conditions are obtained.
  • the density measuring instruments in the inflow duct and outflow duct enable the changes in density due to gassing to be determined and allow for the measurement of the effective gas content of the charged reactant after the gassing process.
  • the computer and control apparatus enables the measured values to be compared with the required values, taking into account the initial conditions of density, temperature and pressure.
  • the computer and control apparatus transmits a command to the drive of the hollow stirrer by way of the speed regulator to vary the speed of rotation as required so that the effective gas content will be kept constant.
  • a temperature measuring instrument connected to the computer and control apparatus by a pulse lead is also preferably provided.
  • a pressure measuring instrument connected to the computer and control apparatus by a pulse lead is also preferably provided. Any changes in the operating temperature and pressure large enough to significantly affect the density and hence the gas content can thereby be taken into account by a variation in the speed of rotation.
  • the interface between the gas cushion and the region in which the component is situated is smaller than the cross sectional area of the region of the component at the level of the stirrer blades of the hollow stirrer. Diffusion between the gas cushion and the reactant is thereby almost completely eliminated.
  • This reduction in the interface area may advantageously be obtained by using a floating lid covering the major part of the interface.
  • the gassing tank has a smaller diameter in the region of the liquid level than in the region of the stirrer blades of the hollow stirrer.
  • the stirrer shaft is covered in the region of the reactant by a sleeve fixed to the internal surface of the gassing tank. This sleeve prevents the formation of a funnel.
  • the filling level regulator preferably has two limiting value controls.
  • the liquid level is kept constant between these limiting value controls which operate within a narrow interval.
  • the opening of the inlet pipe is in the form of a wide mouth. This results in a laminar, flat inflow which spreads out over the cross section of the gassing tank and continuously renews the uppermost layer of reactant so that a narrow range of residence times is ensured precisely in the region which is critical for avoiding diffusion.
  • the opening of the supply duct consists of several openings distributed over the circumference of the gassing tank. If a sufficient number of such openings is provided, preferably distributed uniformly over the circumference, a flow in the radial direction towards the stirrer shaft is achieved before it dips down.
  • a flow directed radially to the stirrer shaft is obtained due to the arrangement of the distributor channel on the internal circumference of the tank.
  • the gassed component is continuously supplied to the mixing head by means of the dosing pump.
  • a small storage tank for the gassed reactant is arranged between the gassing tank and the mixing head, as already proposed in German Offenlegungsschrift No. 3,434,443.
  • the gassed reactant in the storage tank may if necessary be circulated through the mixing head or through reversing valves upstream of the mixing head during periods of rest.
  • a conduit 1 extends from a storage tank (not shown) to a mixing head (not shown) by way of a dosing pump (not shown).
  • a gassing tank 2 is arranged between the storage tank and the dosing pump.
  • the portion of conduit leading to the gassing tank 2 is the supply conduit marked by the reference 3 and the portion leading from the tank is the discharge conduit 4.
  • the gassing tank 2 has a hollow stirrer 5 driven by a variable speed drive 6.
  • the hollow stirrer 5 has a gas intake opening 8 operated by suction in the upper region of its stirrer shaft 7.
  • Stirrer blades 9 provided with gas outlet openings 10 are provided at the end of the stirrer shaft 7 in the lower region of the gassing tank 2.
  • a gas supply conduit 11 with shut off valve 12 opens into the upper region of the gassing tank 2.
  • the liquid level 16 of reactant in the gassing tank 2 is kept constant by means of a filling level regulator 13 which has two limiting controls 14, 15.
  • a gas cushion or gas layer 17 is situated above the liquid level 16.
  • the hollow stirrer 5 sucks gas from this layer and disperses it in the reactant situated underneath it.
  • the opening 18 of the supply conduit 3 is arranged just below the liquid level 16.
  • the stirrer shaft 7 is covered by a sleeve 20 in the region of the layer 19 of ungassed component. This sleeve 20 is fixed to the inside of the gassing tank 2.
  • the layer 21 of gassed component forms approximately from the level of the stirrer blades 9 downwards.
  • Density measuring instruments 22 and 23 are arranged both in the supply conduit 3 and in the discharge conduit 4 and are connected to a computer and control apparatus 26 by pulse leads 24, 25.
  • a temperature measuring instrument 27 and a pressure measuring instrument 28 are provided in the discharge conduit 4 and in the density meter 23 and are also connected to the computer and control apparatus 26 by pulse leads 29, 30.
  • the filling level regulator 13 is also connected to the computer and control apparatus 26 by a pulse lead 31.
  • a pulse lead 32 is connected to a servomotor 33 of the shut-off valve 12 for switching the filling level regulator 13 on and off.
  • a pulse lead 34 extends from the computer and control apparatus 26 to the drive 6 of the hollow stirrer 5 by way of a speed control 35.
  • the liquid level 41 of the reactant in the gassing tank 42 is covered by a floating lid 43.
  • the opening 44 is in this case in the form of a wide mouth.
  • openings 53 branch off at regular intervals from a ring duct 51 surrounding the gassing tank 52 and these openings enter the gassing tank 52 just below the liquid level 54.
  • the gassing tank 61 has a smaller diameter in the region of the liquid level 62 than in the region of the stirrer blades 63.
  • the opening 64 is formed by a channel 66 with overflow 67 covering the internal wall 65 of the tank.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Polyurethanes Or Polyureas (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US07/316,381 1988-03-11 1989-02-27 Process and apparatus for charging a liquid reactant with gas Expired - Fee Related US4973608A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3808082 1988-03-11
DE3808082A DE3808082A1 (de) 1988-03-11 1988-03-11 Verfahren und vorrichtung zum beladen mindestens einer fliessfaehigen reaktionskomponente mit gas, insbesondere in geringen mengen, fuer die herstellung von schaumstoffen, insbesondere polyurethanschaumstoffen

Publications (1)

Publication Number Publication Date
US4973608A true US4973608A (en) 1990-11-27

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Country Status (6)

Country Link
US (1) US4973608A (de)
EP (1) EP0332032B1 (de)
JP (1) JPH01275014A (de)
AT (1) ATE66862T1 (de)
DE (2) DE3808082A1 (de)
ES (1) ES2024056B3 (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5061453A (en) * 1988-05-28 1991-10-29 Bayer Aktiengesellschaft Apparatus for the continuous charging of a liquid reactant with gas for the production of a foamable, liquid reaction mixture
DE4119966A1 (de) * 1991-06-18 1993-01-07 Spuehl Ag Messeinrichtung zur erfassung der gasbeladung einer kunststoffkomponente
DE4233289A1 (de) * 1992-10-02 1994-04-07 Beiersdorf Ag Hydrophile Polyurethanschaumgele und Verfahren zu deren Herstellung
US9284428B2 (en) 2009-07-10 2016-03-15 Huntsman International Llc Crystalline foam
US11319399B2 (en) 2015-11-26 2022-05-03 Webasto SE Device and method for preparing a liquid polymer blend

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0565974B1 (de) * 1992-04-03 1995-08-09 Koepp Aktiengesellschaft Verfahren zur kontinuierlichen Steuerung der Zellenzahl von Polyurethan-Schaumstoffen
DE4235970C1 (de) * 1992-10-26 1993-11-25 Bayer Ag Vorrichtung zum Herstellen eines Schaumstoff bildenden Reaktionsgemisches

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3434443A1 (de) * 1984-09-19 1986-03-20 Bayer Ag, 5090 Leverkusen Vorrichtung zum kontinuierlichen herstellen eines fliessfaehigen, schaumstoffbildenden reaktionsgemisches aus fliessfaehigen komponenten
EP0175252A2 (de) * 1984-09-19 1986-03-26 Bayer Ag Verfahren und Vorrichtung zum Herstellen eines fliessfähigen, zu Schaumstoff ausreagierenden Gemisches aus fliessfähigen, in Vorratsräumen gelagerten Komponenten
US4590218A (en) * 1985-06-19 1986-05-20 The O'brien Corporation Method and apparatus for forming a chemical composition from cross-linking components and product of the method
US4764536A (en) * 1986-01-24 1988-08-16 Maschinenfabrik Hennecke Gmbh Process and apparatus for the preparation of a free-flowing mixture made of free-flowing components which reacts to form foam
US4777186A (en) * 1987-05-04 1988-10-11 Scotfoam Corporation Restricted expansion foaming and the flexible polyurethane foam thereby produced

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* Cited by examiner, † Cited by third party
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DD120830A1 (de) * 1975-07-29 1976-07-05
DE3244037A1 (de) * 1982-11-27 1984-05-30 Bayer Ag, 5090 Leverkusen Verfahren und vorrichtung zum herstellen eines fliessfaehigen, zu schaumstoff ausreagierenden gemisches aus fliessfaehigen komponenten
DE3502071A1 (de) * 1985-01-23 1986-07-24 Battenfeld Maschinenfabriken Gmbh, 5882 Meinerzhagen Ruehrwerk

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3434443A1 (de) * 1984-09-19 1986-03-20 Bayer Ag, 5090 Leverkusen Vorrichtung zum kontinuierlichen herstellen eines fliessfaehigen, schaumstoffbildenden reaktionsgemisches aus fliessfaehigen komponenten
EP0175252A2 (de) * 1984-09-19 1986-03-26 Bayer Ag Verfahren und Vorrichtung zum Herstellen eines fliessfähigen, zu Schaumstoff ausreagierenden Gemisches aus fliessfähigen, in Vorratsräumen gelagerten Komponenten
US4590218A (en) * 1985-06-19 1986-05-20 The O'brien Corporation Method and apparatus for forming a chemical composition from cross-linking components and product of the method
US4764536A (en) * 1986-01-24 1988-08-16 Maschinenfabrik Hennecke Gmbh Process and apparatus for the preparation of a free-flowing mixture made of free-flowing components which reacts to form foam
US4777186A (en) * 1987-05-04 1988-10-11 Scotfoam Corporation Restricted expansion foaming and the flexible polyurethane foam thereby produced

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Kunststoffe, 1984, No. 11, pp. 659 660. *
Kunststoffe, 1984, No. 11, pp. 659-660.

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5061453A (en) * 1988-05-28 1991-10-29 Bayer Aktiengesellschaft Apparatus for the continuous charging of a liquid reactant with gas for the production of a foamable, liquid reaction mixture
DE4119966A1 (de) * 1991-06-18 1993-01-07 Spuehl Ag Messeinrichtung zur erfassung der gasbeladung einer kunststoffkomponente
US5285674A (en) * 1991-06-18 1994-02-15 Spuhl Ag Measurement device for detecting gas charge of a plastic component
DE4233289A1 (de) * 1992-10-02 1994-04-07 Beiersdorf Ag Hydrophile Polyurethanschaumgele und Verfahren zu deren Herstellung
US9284428B2 (en) 2009-07-10 2016-03-15 Huntsman International Llc Crystalline foam
US11319399B2 (en) 2015-11-26 2022-05-03 Webasto SE Device and method for preparing a liquid polymer blend

Also Published As

Publication number Publication date
EP0332032A1 (de) 1989-09-13
DE58900248D1 (de) 1991-10-10
ATE66862T1 (de) 1991-09-15
EP0332032B1 (de) 1991-09-04
DE3808082A1 (de) 1989-09-21
JPH01275014A (ja) 1989-11-02
ES2024056B3 (es) 1992-02-16

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Owner name: BAYER AKTIENGESELLSCHAFT, GERMANY

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Effective date: 19941130

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Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362